At the time I’m writing this I’ve made five complete pairs of shoes (and a couple of completely written off attempts). The second shoe of the latest pair was the first one I have looked at and thought of as a competent piece of apprentice level work where all the basic techniques were there and executed without major screwup. This isn’t to say I’m good at this yet, just that I’m starting to be able to build things without making major mistakes.
My first pair were made about six years ago now but for most of the intervening time I was being slack and making less than a pair a year. My fourth and fifth pair I made in fairly quick succession and the increase in both knowledge and skill I gained in making those two in four months was vastly more than the increase in skills between the first and third pair, which were made over the course of four or five years.
Building shoes isn’t a skill in itself. It is a craft built on a diverse collection of individual skills and the only way to master those skills is to practice and understand each of them. Individually some are harder than others, but ultimately it all just comes down to manual dexterity and muscle memory, so practice on scraps even when you’re not making shoes, and keep those practice pieces.
Write the date on them and save them to look back on so you can see how you’re improving, and if there’s a technique giving you real problems take the practice piece to an event and see if you can find someone who can help you. More than once I have struggled for ages with a technique only to have all of my problems with it erased by 30 seconds of instruction from someone who knew what they were doing.
The other thing to do is when you work out what went wrong with a piece, write it down and keep that with the piece. If you do this you will be able to recognise it better if it starts to go wrong again, and you’ll have a valuable teaching tool to show others.